Preheat oven to 350 degrees and spray a 13x9 baking dish with pam baking spray
In a large mixing bowl, whisk together the pumpkin puree, evaporated milk, eggs, brown sugar, sugar, vanilla, and pumpkin pie spice until smooth and combined
Pour batter into the baking dish
Sprinkle the cake mix evenly onto the batter and lightly press the cake mix into the batter
Sprinkle the chopped pecans onto the cake mix
Drizzle the melted butter onto the cake mix
Bake in the oven for 40 minutes
Check and see if the cake is still jiggly. If so, cover with foil and bake for another 10 minutes
If the cake is set and doesn't jiggle as much, remove from the oven and allow to cool completely